Pulsating combustion process and burner apparatus



y 4, 1967 F. SEEWALD ETAL 3,328,956

PULSATING COMBUSTION PROCESS AND BURNER APPARATUS Filed March 50, 1966 4 Sheets-Sheet 1 y 4, 1967 F. SEEWALD ETAL 3,

PULSAIING COMBUSTION PROCESS AND BURNER APPARATUS Filed March 30, 1966 4 Sheets-Sheet 2 Fig. 2

I July 4, 1967 F. SEEWALD ETAL 3,328,956

PULSATING COMBUSTION PROCESS AND BURNER APPARATUS Filed March 30, 1966 4 Sheets-Sheet 5 y 4, 1967 F. SEEWALD' ETAL 3,323,956

PULSATING COMBUSTION PROCESS AND BURNER APPARATUS Filed March 30, 1966 4 Sheets-Sheet 4 3,328,956 PULSATING COMBUSTION PROCESS AND BURNER APPARATUS Friedrich Seewald and Lukas Siencnik, both of Aachen, Germany, assignors to Wilhelm Kiisters, Eberburgweg, Germany Filed Mar. 30, 1966, Ser. No. 541,473 Claims priority, application Germany, Apr. 1, 1965, S 96,326 13 Claims. (Cl. 60-39.!)6)

This invention relates in general to a pulsating combustion process and burner apparatus therefor of the type wherein a combustion supporting gaseous charge is introduced into the intake of a combustion chamber, and fuel is injected into said gaseous charge for explosive combustion therewith within the chamber, resulting in a pressure rise within the chamber and the forcible expulsion of combustion products from the exhaust of said chamber, followed by a pressure drop in the combustion chamber induced by the momentum of such expelled gases, and then by the introduction of a fresh gas charge into the chamber for repeating the combustion cycle. In general, this combustion process is known in the prior art as disclosed for example by German Patent 523,655, and as more commonly exemplified by the pulse jet engine for the German V-l missile.

In such prior art pulsating combustion processes and burner apparatus, certain problems were encountered in achieving suitable ignition of the fuel injected, to the extent that generally a spark ignition means was required, or in the absence of such positive ignition means, a critical control over the fresh gas charge introduction cycles was required.

One of the advantages of the invention lies in the fact that it provides a pulsating combustion cycle operation similar to that of the Diesel internal combustion engine. According to the invention, the combustion-supporting gas is preheated to a temperature which causes spontaneous ignition of the fuel injected into a combustion chamber containing a charge of the gas, thereby dispensing with the need for any other ignition means.

In the operation of certain prior art pulsating combustion burners, the combustion chambers became hot enough to raise the temperature of incoming gas charges to a level suflicient for spontaneous fuel ignition with the aid of additional heating induced by the pressure wave and temperature of the backwash combustion products of the previous combustion cycle. However, such prior art spontaneous ignition required that the gas charge introduction and fuel injection for each combustion cycle be performed in a precise timing sequence related to the combustion frequency established by the dimensions of the combustion chamber. Since the combustion-supporting gas charge in the combustion chamber would not be hot enough for fuel ignition until the arrival of the backwash pressure wave, a very close coordination of fuel injection was required. Furthermore, in the operation of such prior art pulsating combustion burners, the removal of energy, such as by heat transfer, or by coupling the exhaust outlet to drive a turbine, seriously affected the fuel ignition to the extent that such burners became impractical for use in stationary power plants. Even moderate exhaust back pressures imposed serious limits upon the attainable combustion gas flow rate, there-by rendering such burners unsuitable as gas generators for turbines.

The invention provides for externally preheating the combustion-supporting gas, either independently or by heat derived from the combustion chamber, so that the aid of previous combustion cycle backwash is not required to achieve spontaneous fuel ignition. Consequently, the

. United States Patent ice combustion cycle and burner apparatus of the invention can be controllably operated at various combustion gas generation rates and back pressures so as to make it practical forpower generation. With the invention, no longer must the combustion cycle timing be run in strict accordance with the resonant frequency of the combustion chamber.

As used herein to describe the pulsating combustion process and' operation of the burner according to the invention, the terms combustion-supporting gas and fuel generally signify any two components which react exothermically with each other when in admixture at an ignition temperature, and which by themselves are incapable of any exothermic chemical reaction. For example, the combustion-supporting gas can be air, and the fuel can be gasoline, oil, or in general any substance which is combustible with air. However, the invention is not limited to such commonly designated fuel and combustion-supporting components, but is also applicable to other exothermically reacting fuel and oxidizer combinations, such as hydrogen and fluorine, hydrogen peroxide and kerosene, etc.

In general, it is contemplated that the combustion referred to herein is the result of an exothermic chemical reaction of one substance which is chemically oxidized and another substance which functions as an oxidizer and which is chemically reduced as a result of such combustion. As can be appreciated by the artisan, the combustion supporting component can be a gas or a vapor as can be the fuel component which is injected into the combustion chamber in a finely divided form, such as liquid droplets, vapor, or even a sprayed powder. Likewise in the process and apparatus of the invention, the fuel component' can be introduced first into the combustion charnber and then the oxidizer component injected therein, or vice versa.

It is therefore an objection of the invention to provide a pulsating combustion process wherein spontaneous ignition of the fuel occurs in each combustion cycle upon injection of the fuel into a combustion chamber.

Another object of the invention is to provide a pulsating combustion process, as aforesaid, which can be selectively varied as to the rate of combustion product generation.

A further object of the invention is to provide a pulsating combustion process, as aforesaid, which is substantially independent of the combustion chamber dimensions.

A further object of the invention is to provide a pulsating combustion process, as aforesaid, which can be operated at a selected combustion product generation rate over a Wide range of exhaust back pressures.

A further object of the invention is, to provide a burner apparatus for performing the aforesaid pulsating combus tion process.

A further object of the invention is to provide a burner apparatus, as aforesaid, having a plurality of combustion chambers supplied with combustion-supporting gas and fuel in a continuous cyclical sequence for greater output and thermal efficiency.

A further object of the invention is to provide a burner apparatus, as aforesaid, in which preheating of the combustion-supporting gas is accomplished externally of the combustion chamber from heat at least partially derived therefrom. I

A further object of the invention is to provide a burner apparatus, as aforesaid, having a rotary intakevalve means controlling the admission of combustion-supporting gas to each combustion chamber and driven by the flow of such gas through said intake valve.

Still another and further object of the invention is to provide a burner apparatus, as aforesaid, wherein the fuel Patented July4, 1967 is injected into each combustion chamber by a nozzle carried by the rotary intake valve means.

Other and further objects and advantages of the invention will become apparent from the following detailed description and accompanying drawings in which:

FIG. 1 is a schematic illustration of a pulsating combustion burner of the type used in the prior art;

FIG. 2 is a schematic illustration, partly in section, of a pulsating combustion burner according to a preferred embodiment of the invention;

FIG. 3 is a schematic illustration of the burner shown in FIG. 2 as viewed at a section taken along line II therein;

FIG. 4 is a schematic illustration, partly in section, of a pulsating combustion burner according to another embodiment of the invention;

FIG. 5 is a schematic illustration of the burner shown in FIG. 4 as viewed at a section taken along line IIII therein;

FIG. 6 is a schematic illustration, partly in section, of a pulsating combustion burner according to a further embodiment of the invention; and

FIG. 7 is a schematic illustration of the burner shown in FIG. 6, as viewed along the direction indicated by line III-III therein.

The operation of the basic pulsating combustion process can be simply explained with the aid of FIG. 1, which illustrates a typical prior art burner apparatus having a tubular combustion chamber B. At the intake end B of the combustion chamber B, fresh charges of combustion-supporting gas, such as air, are introduced, one per combustion cycle, through flapper intake valves F, which are either positively controlled by external means (not shown) or are automatically operated in the nature of check valves so as to permit air flow only into the combustion chamber B and to block the escape of any combustion products therefrom through the inlet E.

At the region of the intake end B, a fuel injection nozzle N is located and extends into communication with the interior of the combustion chamber B. The other end of the combustion chamber tube B, namely its exhaust outlet end A, is open to discharge the gaseous products of combustion therefrom. However, the exhaust outlet A can be provided with a valve device (not shown) installed thereat which is operable to close said exhaust outlet A during combustion of the fuel-air mixture, so as to achieve a constant-volume type of combustion.

In the typical operation of the combustion chamber B, air enters through the flapper valves F, fuel is injected by the nozzle N, into this air charge, an explosive combustion is initiated, and the pressure within the chamber B rises. The expanding combustion product gases close the flapper valves F and discharge through the exhaust outlet A at a high velocity and produce a thrust. The momentum of the exhausting gases produces a pressure drop within the chamber B to below the ambient atmospheric pressure so that consequently a new charge of air is introduced through the valves F and the combustion cycle is repeated.

In such a pulsating combustion cycle, the combustion product gases will be accelerated out through the exhaust outlet A as long as an over-pressure exists within the chamber B. At the instant when such a quantity of combustion gas has been discharged that the pressure within chamber B has dropped back to the ambient atmospheric pressure, maximum exhaust velocity is attained. However, due to the momentum of the exhaust gases, their movement continues, thereby further reducing the pressure within the chamber B below atmospheric pressure to the extent that the intake valves F open, either automatically or by a control means (not shown), and a fresh charge of air is drawn into the chamber B by suction.

However, the reduction of pressure within the chamber B acts to retard the outward flow of the exhaust gases, and finally when the pressure within the chamber B is below atmospheric pressure, a portion of these exhaust gases are sucked back into the combustion chamber B, and constitute a backwash gas fiow. As a result of this backwash, an over-pressure again develops in the combustion chamber B. Upon the arrival of the backwash, the intake valves F must close, since otherwise the fresh air charge would be driven either completely or partially back out of the chamber B under the action of the backwash over pressure forces. The inertia of these backwash and fresh air charge gases, which then flow towards the closed intake end E, produce within the combustion chamber B another pressure rise and a compression of the fresh air charge that has been admitted, this pressure rise and the gas mixture temperature resulting therefrom aids in initiating combustion of the forthcoming cycle. As is generally known, this pressure rise takes place in the form of pressure waves which pass through the gaseous contents of the combustion chamber B with the velocity of sound.

When such a combustion cycle has been repeated several times with the ignition of the fuel-air mixture by a supplemental ignition means, such as an electric spark, the combustion chamber B becomes hot to the extent that subsequent combustion cycles can be accomplished automatically without any supplemental spark ignition. This automatic ignition is brought about due to the vigorous mixing movements which occur in the fresh air charge during the intake portion of the cycle when it mixes with the hot, partially still burning combustion gas residue remaining in the chamber B from the preceding cycle. As a result of such mixing, all components of the new charge are brought into contact with the wall of the chamber B and other internal parts thereof heated by previous combustion cycles. By reason of these two heating influences, a fairly uniform heating of the entire combustion chamber B gas contents results. If the quantity of heat yielded by the chamber wall or by the hot gas residues to the new charge is sufiiciently great, then, but only then, the relatively small pressure rise induced by the backwash pressure wave will produce a resultant gas temperature sufiicient to ignite the gas and fuel mixture when the fuel is injected, thereby propagating combustion at high speed through the chamber B.

It can be seen from this that ignition at the proper moment, namely upon the arrival of the backwash pressure Wave, and the rapid propagation of the combustion through the entire combustion chamber B, which again takes place when the pressure Wave runs through the combustion chamber B, substantially hinges upon two requirements.

First, heat must be yielded by the tube wall etc. to each incoming air charge that its temperature is raised to approximately the ignition temperature of the ultimate fuel-air mixture.

Secondly, this heat transfer must be completed in the very short time that is available until the pressure wave originating from the expansion of the combustion gases in the preceding cycle enters the combustion chamber.

The time that is required in order to raise all of the fresh air charge in the combustion chamber to the necessary temperature depends, on the one hand, on the tube walls having a certain minimum temperature, and on the other hand it depends on the length of the mixing paths and hence upon the diameter of a tubular combustion chamber B. The time of the arrival of the backwash pressure wave is established by the resonant frequency of the combustion chamber tube B and depends substantially upon its length.

So, in order for the mixture in the combustion chamber B to be sufliciently heated up at the moment in which the backwash pressure wave arrives, the length and the diameter of the tube must be coordinated with one another.

Once the length of the tube B has been fixed, then the operating combustion cycle frequency also is fixed, and as long as the ignition and combustion are brought about in the above-described manner, very little can be done to shift this frequency since if any significant frequency shift were attempted, the heating and ignition would no longer occur in the correct time sequence, and would cause the tube to cease operating as a pulsating combustion chamber.

However, not only is the frequency range held within narrow limits in the pulsating combustion tube B of the prior art, which all operate by the process described, but additionally any removal of energy greatly interferes With the operation of the process.

One especially important type of energy removal, on which there are a large number of patents and publications, is the use of the pulsating combustion tube as a source of compressed gas which can be used to operate a gas turbine (not shown). This assumes that, at the exhaust end of the combustion tube, a higher pressure prevails than at the inlet. Accordingly, for successful utilization as a pressure gas generator, reliable operation of the pulsating combustion tube at a back pressure that suflices to operate economically a gas turbine, is required. Even in the case of small back pressures imposed upon a combustion tube of the prior art, the combustion gas output drops rapidly and, before reaching back pressure levels which might be of interest for practical power generation applications, the combustion operation is halted.

The pulsating combustion tube B of the prior art and those of the patents or proposals thus far known represent pulsating combustion burner apparatus that, on account of their excessively poor efiiciency, are not competitive with stationary burners presently in use. Furthermore, due to their poor regulatability and insufficient adaptability to the changing conditions of practice, their practical value is still futher reduced to such an extent that successful application has been achieved in no field of the art, with the exception of certain special military applications.

It is the aim of the invention to eliminate these deficiencies inherent in prior art pulsating combustion burners. For this purpose, the invention provides a process for the operation of one or more pulsating combustion tubes wherein the ignition and the ignition timing of the reacting gas mixture is relatively independent of the operating conditions and dimensions of the combustion chamber. The process of the invention is characterized in that the fresh combustion-supporting charge that flows in during the charging portion of the combustion cycle at first consists only of those components of the combustible mixture which do not react with one another under the given operating conditions, and is heated before or during the intake process to such a temperature that, upon the addition of the components still lacking, the combustion reaction reliably and spontaneously takes place. The still unignitable charge is thus not heated merely in the inevitable way described above, by the hot tube wall and by mixture with hot gas residues, but instead additional heat is added to it before and/or during its flow into the combustion chamber, and at least so much heat is added that the said first component charge reaches the mixture ignition temperature, so that after the remaining component or components of the mixture are introduced into the combustion chamber, spontaneous ignition and combustion will take place with certainty, without requiring the additional action of the backwash pressure wave.

The difference between the pulsating burner tube of the prior art process of operation and the combustion tube operated according to the new process can be approximately equated with the difference between Otto-cycle and Diesel-cycle engines. In the Otto-cycle engine, after the intake and compression of the mixture have been completed, ignition is additionally required. In the Diesel-cycle engine, the temperature is so elevated by high compression of the air charge that, when the fuel is injected, ignition reliably takes place. The role which is played by the ignition spark in the Otto-cycle engine is played in the prior-art pulsating combustion tube, such as the Schmidt tube, by the above-mentioned pressure wave. According to the new process of the invention, the cooperation of the pressure wave is not necessary because the fresh oxidizer gas is so heated that ignition and combustion reliably occur evenwithout the pressure Wave.

In order to explain the operation of a combustion tube according to the invention by means of an example, let it be assumed that plain air flows into the combustion chamber after having been preheated to a temperature of, for example, 600 C. At that time, before the fuel is fed in, such air by itself cannot be ignited either by further heating or by pressure waves. Not until the instant the fuel is injected does ingnition take place, but then it takes place reliably and independently of all other operating conditions. Instead of air and fuel, any other combination of substances capable of exothermic chemical reaction, such as hydrogen and fluorine, or hydrogen peroxide and kerosene, etc., can be used.

Accordingly, by the process of the invention it is brought about that the moment in each cycle at which the combustion takes place is determined, not as in the prior art processes described previously, by the design of the tube, but rather it can be selected freely within wide limits by the appropriate controlling of the time of the fuel injection. Furthermore, it is possible by increasing the back pressure and also by varying the operating frequency of the tube by changing its length, to vary the combustion gas output within wide limits, without thereby impairing the reliability of the ignition and the quality of the combustion. A combustion chamber operating on this principle is thus controllable over a correspondingly Wide range. Furthermore, it can be made to operate at a higher back pressure without the danger of ignition failure.

One or the other of the possibilities otfered can be utilized to a greater or lesser extent, depending on the desired application.

If it is desired to make full use of the range of control, it is recommendable to use not automatic intake valves but controlled intake valves, for which the time of opening and closing can be adjusted independently of any vibrational properties or natural frequencies of the combustion chamber.

If a plurality of similar combustion chambers are combined into a unit, the same auxiliary equipment, such as preheater, control system, injection system, etc. can be used in whole or in part for all or several of these combustion chambers.

Since the amount of heat needed for the pro-heating is used entirely to the benefit of the combustion gases produced, it does not entail any additional heat consumption. Insofar as possible, waste heat which otherwise would be lost can be used in whole or in part for the preheating, thereby achieving, in addition to the above-described advantage -of controllability, an improvement in thermal efiiciency.

If it is also desired to eliminate or mitigate the abovementioned disadvantage that, when operating against back pressure, the intake is impaired and with it the amount of heating gas produced in the tube, the process that has been explained (operation with preheating) can be combined with an improvement of intake in the charging portion of the cycle by supercharging.

, As already explained above, the precompression of the entering gas by means of a supercharging compressor has previously been proposed. The expense of such a combustion chamber and supercharger is, however, comparable to that of steadily operating burners of conventional type.

However, this expense can be kept substantially low by compressing only a portion rather than all of each aspirated fresh charge. Thus the combustion chamber is made to aspirate, in the automatic manner described above, as much fresh charge as is possible at the prevailing back pressure. Towards the end or after the end of this intake process, the charge is then supplemented by forcing into the combustion chamber by means of a compressor the desired additional amount of charge. By this reduction of the quantity that has to be precompressed, the compressor and the power required to drive it become small. This creates the possibility of combining it with the other apparatus elements that are also needed, such as the controlling means, and driving it in unison with the latter.

As an example of how the process explained above can be practically realized, a pulsating combustion burner 10 according to the invention is represented in FIGS. 2 and 3, which show a combustion chamber B with conventional automatic intake valves F, wherein the preheating of the gas aspirated through the intake duct P is accomplished by the fact that this gas passes around the combustion tube B, which can be provided with cooling fins (not shown).

In FIGS. 4 and 5 there is shown a pulsating combustion burner according to another embodiment of the invention in which the preheating is performed by a separate gas heater (not shown) of any suit-able conventional type. In this case, therefore, previously heated gas or hot air, as the case may be, flows in through the duct Z. A rotary intake valve having a disk St provided with one or more openings G, hereinafter called control slits, which slide over the intake opening E or openings of the combustion chamber B or combustion chamber B when the disk St is rotated, and uncover these intake ports E for admitting gas charges to each chamber B in continuous cyclical succession.

If rotating parts of this kind, such as the control disk St, are provided, the fuel line L and the injection nozzle D can be allowed to rotate with this disk. Then, due to centrifugal action in the radial part of the fuel line L, the pressure is developed ahead of injection nozzle D which is required for the injection. In this manner the need for a fuel pump can be eliminated.

In FIG. 4 is schematically represented pulsating combustion burner embodiment with variable effective combustion tube B' length. The outer telescoping tube portion T can be extended to various distances beyond the end of the burner tube B, thus varying the effective tube B length and the natural frequency.

FIGS. 6 and 7 show by way of example another embodiment in which a number of combustion chambers B are combined into a unit. As shown in FIGS. 6 and 7, the combustion chambers B are so arranged in series that together they form the wall of a cylindrical tube. The preheating which can be done by separate gas heaters ahead of the intake Z or in some other manner, as for example within the unit itself as in FIG. 2, has been omitted for greater clarity. The control valve disk St with the control slit G or control slits, and with the fuel conduit L and injection nozzle or nozzles D, can in this case be arranged as in the case of the single tube represented in FIGS. 4 and 5. The same means which suplpy a combustion tube as in FIGS. 4 and 5 can here be made to supply several or all of the tubes by appropriately selecting the rotation speed. For the fuel injection there is the possibility, as shown in FIGS. 6 and 7, of economizing not only the fuel pump but also the system for controlling the injection process, The fuel can flow constantly through the conduit L and the injection nozzle D, and does not have to be interrupted since the combustion tubes B lie directly beside one another. It is necessary only to adjust the rate of fuel delivery so that the desired quantity of fuel comes out in the period in which the injection nozzle D passes over a combustion tube port.

In order additionally to promote the occurrence of ignition at the desired moment, is expedient to keep the entire combustion burner and all the combustion chambers B and parts thereof as hot as possible. This can be done in the case of the example shown in FIGS. 6 and 7 simply "by fixedly combining a portion B of the combustion chamber with the disk St for rotation with the 8 latter. This portion B1 of the combustion chamber then participates in close succession in the combustion processes of all combustion chambers B and becomes correspondingly hotter. Such a system is indicated by way of example in FIGS. 6 and 7.

Simultaneously, but independently of the fore-going, there is provided in FIGS. 6 and 7 means for increasing the efficiency of the combustion chamber or chambers by supercharging with compressed gas or air, as the case may be, especially in the case of back pressure beyond the degree that can be achieved in the charging cycle in pulsating tubes by the use of the gas vibrations alone in the prior art manner.

A passage K corresponding to the bucket trough of a turbocompressor is created in the control valve disk St, the intake opening of said passage K being concentric with the disk St, and the discharge opening wiping over the intake port or ports of the combustion tube or tubes. As long as the discharge opening of passage K rotating with control disk St is wholly or partially opposite a combustion tube B, the gases or air compressed in the rotating passage K flow into the combustion chamber which already contains a charge which has flowed in through the control slit G under the effect of the gas vibration process.

The driving of the above described controlling members and the operation of the injection line combined therewith and of the compression passage can be performed by an outside drive. These members, however, can also be driven by a turbo drive arrangement consisting of individual vanes Sch or of a bucket wheel which is hit by the gases flowing into each combustion chamber B.

As indicated in FIG. 7, buckets or vanes Sch are provided in the control slit G, which like the buckets of turbines deflect the flowing gases. In this manner the flow produces a force which sets the wheel and the disk combined with it into rotation. The rotary speed of the disk can be regulated, as is customary in turbines, by guiding mechanisms or other methods of varying the flow, or by increasing the mechanical work which the disk has to perform by connecting a work-dissipating apparatus to it, such as a dynamo for the production of electrical energy.

From FIGS. 6 and 7, it can be appreciated that the preheated combustion-supporting gas can be supplied to each of the chambers B in succession by the duct Z and/or the duct Z Gas from duct Z flows directly through the control aperture G into each combustion chamber B" as the disk St rotates. Gas from duct Z flows through the radial passage K into the aperture G and thence into the combustion chambers B, and is delivered at a supercharging pressure by reason of centrifugal compression in passage G resulting from the rotation of the disk St.

The ducts Z and Z can be expediently connected to receive preheated gas from a common duct (not shown), which is either heated itself or is arranged to pass its gas flow through a preheating apparatus (not shown).

If supercharging is not desired, the duct Z and associated radial passage K can be omitted.

As shown in FIG. 6, the disk St has a somewhat substantial thickness, and such thickness can be utilized to advantage to raise the effective temperature of the several combustion chambers B. If one or more cavities are machined into the disk St, preferably blind cavities, and arranged so as to define an extended portion of each combustion chamber as the disk S! is rotated to position such cavity or cavities into adjoining relation with the inlet of each successive chamber B, the effective temperature of said chambers B will be raised because the cavity portions participate in each combustion process in all combustion chambers B of the group.

As can be appreciated from the foregoing description of the invention in terms of certain of its embodiments, the pulsating combustion process and burner apparatus of the invention is susceptible of numerous modifications and variations which will become obvious to the artisan. How ever, the scope of the invention is intended to be limited only by the following claims wherein we have endeavored to claim all inherent novelty.

We claim:

1. In a pulsating combustion process of the type wherein a combustion supporting gaseous charge is introduced into the intake of a combustion chamber, and fuel is injected into said gaseous charge for explosive combustion therewith within the chamber, resulting in a pressure rise within said chamber and the forcible expulsion of gaseous combustion products from the exhaust of said chamber, followed by a pressure drop in the combustion chamber induced by the momentum of such expelled gases, and then by the introduction of a fresh gaseous charge into the chamber for repeating the combustion cycle, the improvement which comprises preheating the gaseous charge to an elevated temperature which, after introduction into the combustion chamber, said gaseous charge spontaneously ignites the fuel injected into the chamber.

2. The improvement according to claim 1 wherein at least a portion of the preheated gaseous charge is introduced into the combustion chamber at a supercharging pressure.

3. The improvement according to claim 1 wherein a portion of the heat generated by each preceding combustion cycle is transferred to the fresh gaseous charge for the forthcoming combustion cycle to preheat said fresh charge prior to introduction into the combustion chamber.

4. In a pulsating combustion process of the type Wherein a combustion supporting gaseous charge is introduced into the intake of a combustion chamber, and fuel is v injected into said gaseous charge for explosive combustion therewith within the chamber, resulting in a pressure rise within said chamber and the forcible expulsion of gaseous combustion products from the exhaust of said chamber, followed by a pressure drop in the combustion chamber induced by the momentum of such expelled gases, and then by the introduction of a fresh gaseous charge into the chamber for repeating the combustion cycle, the improvement which comprises preheating a combustion supporting gas to an elevated temperature at which spontaneous ignition of the fuel occurs upon injection into a charge of such preheated gas, introducing in repetitive cyclical succession, a charge of said preheated gas into each of a plurality of combustion chambers, and injecting a predetermined quantity of fuel into each of said combustion chambers following the introduction of a preheated gas charge therein for spontaneous ignition and combustion therewith.

5. A pulsating combustion burner apparatus which comprises a combustion chamber having an inlet disposed for receiving charges of combustion-supporting gas for combustion with fuel injected therein, and an exhaust outlet for discharging the gaseous products of such combustion, intake valve means interposed in the gas flow path to the inlet of said combustion chamber and operable to admit a predetermined gas charge thereto during each pulsating combustion cycle, means defining a nozzle disposed for communication with a source of fuel and for communication with said combustion chamber to inject a predetermined quantity of fuel therein during each combustion cycle, and a duct disposed for communication with a combustion-supporting gas source and for communication with said intake valve means for supplying charges of combustion-supporting gas therethrough to said combustion chamber, said duct being disposed to receive heat from said combustion chamber to preheat the gas flowing through said duct to thereby raise the temperature of each gas charge introduced into the combustion chamber to a level which spontaneously ignites the fuel injected into said chamber.

6. The apparatus according to claim 5 wherein a portion of said duct is bounded by the exterior surface of the combustion chamber.

7. A pulsating combustion burner apparatus which comprises at least one combustion chamber having an inlet disposed for receiving charges of combustion-supporting gas for combustion with fuel injected therein, and an exhaust outlet for discharging the gaseous products of such combustion, nozzle means disposed for communication with a source of fuel and for communication with each combustion chamber to inject a predetermined quantity of fuel therein during each pulsating combustion cycle, rotary gas intake valve means interposed in the gas flow path to the inlet of each combustion chamber and disposed for rotation relative thereto, to admit a predetermined gas charge thereto during each combustion cycle, a duct disposed for communication with a combustion-supporting gas source and for communication with said rotary intake valve means for supplying charges of combustion-supporting gas therethrough to each combustion chamber, and means for preheating the gas supplied through said duct to raise the temperature of each gas charge introduced into each combustion chamber to a level which spontaneously ignites the fuel injected therein.

8. The apparatus according to claim 7 wherein said rotary intake valve means includes a disk member having an. aperture and disposed for rotation relative to each combustion chamber in wiping contact with the inlet thereof to admit through said aperture a combustion supporting gas charge for each combustion chamber in continuos cyclical succession, and to block the escape of combustion products through the inlet of each combustion chamber.

9. The apparatus according to claim 8 including at least one blade member supported by said disk member and disposed across the aperture thereof for reaction with the gas flow therethrough to rotatably drive said disk member.

10. The apparatus according to claim 8 wherein said nozzle means includes a nozzle supported by said disk member for rotation therewith and disposed for extension within the aperture thereof to inject fuel into each combustion chamber along with the gas charge introduced therein through said aperture.

11. The apparatus according to claim 8 including means defining a radial passage extending through said disk member and disposed for communication with said aperture and for communication with said duct to pass preheated combustion-supporting gas into each combustion chamber in succession, and to centrifugally compress said gas to a supercharging pressure by the rotation of said disk member.

12. The apparatus according to claim 8 wherein each combustion chamber is generally tubular and has a length portion disposed for telescopic movement with respect to the remaining portion of the combustion chamber to accommodate selective adjustment of the effective overall length of the combustion chamber.

13. The apparatus according to claim 8 wherein said disk member has at least one cavity disposed to define a portion of each combustion chamber as the disk is rotated to position said cavity in communication with the inlet of each combustion chamber in succession.

References Cited UNITED STATES PATENTS 2,594,765 4/1952 Goddard 60247 2,659,198 11/1953 Cook 60-247 2,671,314 3/1954 Lichty 6039.51 X 2,795,104 6/1957 Zinner 60247 X 2,937,500 5/1960 Bodine 60247 X 2,942,412 6/ 1960 Bollay 60247 CARLTON R. CROYLE, Primary Examiner. 

1. IN A PULSATING COMBUSTION PROCESS OF THE TYPE WHEREIN A COMBUSTION SUPPORTING GASEOUS CHARGE IS INTRODUCED INTO THE INTAKE OF A COMBUSTION CHAMBER, AND FUEL IS INJECTED INTO SAID GASEOUS CHARGE FOR EXPLOSIVE COMBUSTION THEREWITH WITHIN THE CHAMBER, RESULTING IN A PRESSURE RISE WITHIN SAID CHAMBER AND THE FORCIBLE EXPLUSION OF GASEOUS COMBUSTION PRODUCTS FROM THE EXHAUST OF SAID CHAMBER, FOLLOWED BY A PRESSURE DROP IN THE COMBUSTION CHAMBER INDUCED BY THE MOMENTUM OF SUCH EXPELLED GASES, AND THEN BY THE INTRODUCTION OF A FRESH GASEOUS CHARGE INTO THE CHAMBER FOR REPEATING THE COMBUSTION CYCLE, THE IMPROVEMENT WHICH COMPRISES PREHEATING THE GASEOUS CHARGE TO AN ELEVATED TEMPERATURE WHICH, AFTER INTRODUCTION INTO THE COMBUSTION CHAMBER, SAID GASEOUS CHARGE SPONTANEOUSLY IGNITES THE FUEL INJECTED INTO THE CHAMBER. 